''Naohidemyces vaccinii'' is a

plant pathogen Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like orga ...

that affects members of the ''

Vaccinium ''Vaccinium'' is a common and widespread genus of shrubs or dwarf shrubs in the heath family (Ericaceae). The fruits of many species are eaten by humans and some are of commercial importance, including the cranberry, blueberry, bilberry (wh ...

'' and ''

Tsuga ''Tsuga'' (, from Japanese (), the name of '' Tsuga sieboldii'') is a genus of conifers in the subfamily Abietoideae of Pinaceae, the pine family. The English-language common name "hemlock" arose from a perceived similarity in the smell of it ...

'' genera, causing leaf

rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH) ...

on lingonberries,

blueberries Blueberries are a widely distributed and widespread group of perennial flowering plants with blue or purple berries. They are classified in the section ''Cyanococcus'' with the genus ''Vaccinium''. Commercial blueberries—both wild (lowbush) ...

, and cranberries, and early needle cast on hemlocks. ''Naohidemyces vaccinii'' is found on the ''Vaccinium'' genus in Canada, the United States (AK, ME, NH), the United Kingdom, Europe, Russia, China, Korea, and Japan, and on hemlock in AK, ID, WA in the United States, BC in Canada, and Japan.

Taxonomy

''Naohidemyces vaccinii'' is a

basidiomycete Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basid ...

rust fungi with a number of different synonyms, including '' Pucciniastrum vaccinii'' and ''Pucciniastrum myrtilli'', but was moved to the ''Naohidemyces'' genus due to its dome-shaped covering over the aecia. ''N. vaccinii'' is now thought to be the western form of the fungi, and ''Thekopsora minima'' as the eastern form.

Pathology

''Naohidemyces vaccinii'' causes leaf rust on the leaves of the ''Vaccinium'' host, and

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

and early abscission on both ''Vaccinium'' and ''Tsuga'', to which neither is fatal but can be a drain on fruit yield.

Life cycle

''Naohidemyces vaccinia'' is wind-borne, and initially forms yellow-orange

urediniospore Urediniospores (or uredospores) are thin-walled spores produced by the uredium, a stage in the life-cycle of Rust (fungus), rusts. Development ''Urediniospores'' develop in the uredium, generally on a leaf's under surface. Morphology *Uredinio ...

s in pustulates on the underside of ''Vaccinium'' leaves in midsummer, which reinfect ''Vaccinium'' leaves, building up inoculum for reinfection. This is followed by flat telia crusts in late summer for overwintering, although rarely on lingonberries.

Teliospore Teliospore (sometimes called teleutospore) is the thick-walled resting spore of some fungi (Rust (fungus), rusts and Smut (fungus), smuts), from which the basidium arises. Development They develop in ''telium, telia'' (sing. ''telium'' or ''telio ...

s germinate from telia in spring, from which basidia form, releasing

basidiospore A basidiospore is a reproductive spore produced by basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid Ploidy () is the number of complete sets of chromos ...

s to ''Tsuga'' species. Once alighting on ''Tsuga'' needles in the spring, pyncia are formed. Finally in early summer, yellow-orange aeciospores form in shallow conical aecia on the underside of the needles in two rows following the length of the needle.

Disease impact

Leaf rust is most common on cultivated ''Vaccinium'' and relatively rare in wild populations. It is a relatively benign disease, and has little direct impact on crops, but has become an epidemic in rare occasions, particularly to cultivated blueberries.

Controls

Fungicides have been shown to be effective against ''N. vaccinii'', but not all are registered for blueberries, cranberries, or lingonberries. Applications depend on climate and species, as ''Vaccinium'' that keep their leaves throughout the year may need to be treated far earlier than the first sign of leafing out. Removing ''Tsuga'' or other wild, evergreen ''Vaccinium'' hosts within 0.5 km of crops can be beneficial in breaking the sporulation cycle.

References

{{Taxonbar, from=Q6964527 Pucciniales Fungal plant pathogens and diseases Taxa named by Johannes Baptista von Albertini Taxa named by Lewis David de Schweinitz Fungi described in 1805 Fungi of Asia Fungi of Europe Fungi of North America Fungus species